Temperature Converter

1How to use

1. Type the temperature you have.
2. Choose the scale it is on: Celsius, Fahrenheit or kelvin.
3. The other two appear underneath, each with a copy button. Nothing is shown until the box has a number in it.

💡 Exponents can be entered with e — for example, 1.5×10⁻⁵ is entered as 1.5e-5.

2Formula & notes

Three scales, and the whole difficulty is that they disagree about where zero is and how big a degree is. The kelvin starts at absolute zero; Celsius starts 273.15 K above it and counts in the same size of step; Fahrenheit starts lower still and counts in steps five-ninths as large.

Practical notes

• 273.15 is a definition, not a measurement. JIS Z 8000-5:2014 (ISO 80000-5) 5-2 fixes the Celsius scale as t = T − T₀ with T₀ = 273.15 K exactly, and notes that T₀ sits exactly 0.01 K below the triple point of water. Since the 2019 revision of the SI the kelvin itself is fixed by the Boltzmann constant, and 273.15 stays as the definition of Celsius.
• A temperature and a temperature difference do not convert the same way. This page converts temperatures, which is why it applies the offsets. For a difference, drop them: 1 °C of change is 1 K and 1.8 °F.
• The unit is the kelvin, written K. There is no degree sign on it and it is not capitalised when spelled out.
• Below absolute zero the tool refuses instead of answering. −300 °C is not a very cold temperature; it is not a temperature.
• Water freezing at 0 °C and boiling at 100 °C are where the scale came from historically. Neither defines it now — both are measured values that come out very close to the round numbers, and the boiling point depends on the pressure anyway.

3FAQs